1. Field of the Invention
The present invention relates to a position measuring apparatus that uses a plate-like scale having a grating pattern to measure a position of a measured object. Further, the present invention relates to a pattern transfer apparatus using the position measuring apparatus. In addition, the present invention relates to a device measuring method using the pattern transfer apparatus.
2. Description of the Related Art
A projection exposure apparatus that transfers a circuit pattern formed on an original to a substrate via a projection optical system has been used from the past. In recent years, the demand for a higher-resolution and cheaper exposure apparatus has been being gradually increased. One of the important performances of the exposure apparatus may include a superposition precision when the circuit pattern is transferred to the substrate. Generally, a plurality of circuit patterns are formed on the substrate in a multi layer, however unless the plurality of circuit patterns is aligned with each other in a predetermined precision, an electronic circuit may not be realized.
Therefore, a technology for accurately aligning a substrate at the time of exposure is important. As one of the technologies for aligning a substrate, a position measuring apparatus measuring a position of a moving stage mounted with the substrate by using a plate-like scale having a grating pattern have been discussed.
Japanese Patent Application Laid-Open No. 2009-004737 discusses a position measuring apparatus that includes a scale fixed to a lens barrel surface plate and a sensor fixed on a stage. Further, Japanese Patent Application Laid-Open No. 2009-004737 discusses that the scale is coupled with the lens barrel surface plate via a deflection element.
In the position measuring apparatus, a plurality of deflection elements are arranged on a virtual circle, centered on a central axis of a lens barrel. Each deflection element has flexibility in a diameter direction to prevent the scale from displacing even if the lens barrel is deformed due to a temperature change.
In the exposure apparatus of the related art, the lens barrel surface plate may be supported on a floor surface via an anti-vibration apparatus, such as an air mount, and the like, and therefore vibration transferred from a floor to the lens barrel surface plate may be disregarded. In recent years, however, a precision required for the exposure apparatus has been increased and the vibration that is not completely removed by the air mount to be transferred to the lens barrel surface plate has been concerned.
In particular, in the position measuring apparatus using the scale, the scale is often mounted on a structure, such as the lens barrel surface plate, so that it is concerned that vibration may be transferred to the scale from the structure. In particular, since the scale has a structure easily deformed in a plate thickness direction, a deformation amount may be increased when vibration is transferred in the direction. In this case, even if a vibration frequency is sufficiently smaller than a natural frequency of the scale, an inertial force in response to an acceleration generated in the scale may be applied to the scale, and thus there is fear that the deformation of the scale may be increased.
A position measuring apparatus discussed in Japanese Patent Application Laid-Open No. 2009-004737 has a structure in which a deflection element has flexibility in a diameter direction but a plate thickness direction of the scale is not considered and vibration is easily transferred to the scale from the lens barrel surface plate via the deflection element.